The wheel speed sensor should have resistance when disconnected and checked at the connector, it is best to check them with an oscilloscope but if you jack up the car and spin the wheel it should produce an ac voltage on a voltmeter.

No, you'll need a scan tool that can read the codes in the ABS module.
This car has a very complex computer system, I suggest you take it to a Volvo shop and have them read out all the diagnostic codes in the entire system and check to see how many software updates are available for the vehicle.